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authorLinus Torvalds <torvalds@linux-foundation.org>2016-05-21 08:31:33 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-21 08:31:33 +0300
commit5469dc270cd44c451590d40c031e6a71c1f637e8 (patch)
tree5ca6330c2d754dbe82bfa75964a7f828f364e48f /Documentation
parent2f37dd131c5d3a2eac21cd5baf80658b1b02a8ac (diff)
parentea9b50133ffebbd580cb5cd0aa222784d7a2fcb1 (diff)
downloadlinux-5469dc270cd44c451590d40c031e6a71c1f637e8.tar.xz
Merge branch 'akpm' (patches from Andrew)
Merge more updates from Andrew Morton: - the rest of MM - KASAN updates - procfs updates - exit, fork updates - printk updates - lib/ updates - radix-tree testsuite updates - checkpatch updates - kprobes updates - a few other misc bits * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (162 commits) samples/kprobes: print out the symbol name for the hooks samples/kprobes: add a new module parameter kprobes: add the "tls" argument for j_do_fork init/main.c: simplify initcall_blacklisted() fs/efs/super.c: fix return value checkpatch: improve --git <commit-count> shortcut checkpatch: reduce number of `git log` calls with --git checkpatch: add support to check already applied git commits checkpatch: add --list-types to show message types to show or ignore checkpatch: advertise the --fix and --fix-inplace options more checkpatch: whine about ACCESS_ONCE checkpatch: add test for keywords not starting on tabstops checkpatch: improve CONSTANT_COMPARISON test for structure members checkpatch: add PREFER_IS_ENABLED test lib/GCD.c: use binary GCD algorithm instead of Euclidean radix-tree: free up the bottom bit of exceptional entries for reuse dax: move RADIX_DAX_ definitions to dax.c radix-tree: make radix_tree_descend() more useful radix-tree: introduce radix_tree_replace_clear_tags() radix-tree: tidy up __radix_tree_create() ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/testing/sysfs-block-zram9
-rw-r--r--Documentation/blockdev/zram.txt28
-rw-r--r--Documentation/filesystems/proc.txt1
-rw-r--r--Documentation/vm/transhuge.txt12
-rw-r--r--Documentation/vm/z3fold.txt26
5 files changed, 51 insertions, 25 deletions
diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index 2e69e83bf510..4518d30b8c2e 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -166,3 +166,12 @@ Description:
The mm_stat file is read-only and represents device's mm
statistics (orig_data_size, compr_data_size, etc.) in a format
similar to block layer statistics file format.
+
+What: /sys/block/zram<id>/debug_stat
+Date: July 2016
+Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+Description:
+ The debug_stat file is read-only and represents various
+ device's debugging info useful for kernel developers. Its
+ format is not documented intentionally and may change
+ anytime without any notice.
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 5bda5031c83d..13100fb3c26d 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -59,27 +59,16 @@ num_devices parameter is optional and tells zram how many devices should be
pre-created. Default: 1.
2) Set max number of compression streams
- Compression backend may use up to max_comp_streams compression streams,
- thus allowing up to max_comp_streams concurrent compression operations.
- By default, compression backend uses single compression stream.
-
- Examples:
- #show max compression streams number
+ Regardless the value passed to this attribute, ZRAM will always
+ allocate multiple compression streams - one per online CPUs - thus
+ allowing several concurrent compression operations. The number of
+ allocated compression streams goes down when some of the CPUs
+ become offline. There is no single-compression-stream mode anymore,
+ unless you are running a UP system or has only 1 CPU online.
+
+ To find out how many streams are currently available:
cat /sys/block/zram0/max_comp_streams
- #set max compression streams number to 3
- echo 3 > /sys/block/zram0/max_comp_streams
-
-Note:
-In order to enable compression backend's multi stream support max_comp_streams
-must be initially set to desired concurrency level before ZRAM device
-initialisation. Once the device initialised as a single stream compression
-backend (max_comp_streams equals to 1), you will see error if you try to change
-the value of max_comp_streams because single stream compression backend
-implemented as a special case by lock overhead issue and does not support
-dynamic max_comp_streams. Only multi stream backend supports dynamic
-max_comp_streams adjustment.
-
3) Select compression algorithm
Using comp_algorithm device attribute one can see available and
currently selected (shown in square brackets) compression algorithms,
@@ -183,6 +172,7 @@ mem_limit RW the maximum amount of memory ZRAM can use to store
pages_compacted RO the number of pages freed during compaction
(available only via zram<id>/mm_stat node)
compact WO trigger memory compaction
+debug_stat RO this file is used for zram debugging purposes
WARNING
=======
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 7f5607a089b4..e8d00759bfa5 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -225,6 +225,7 @@ Table 1-2: Contents of the status files (as of 4.1)
TracerPid PID of process tracing this process (0 if not)
Uid Real, effective, saved set, and file system UIDs
Gid Real, effective, saved set, and file system GIDs
+ Umask file mode creation mask
FDSize number of file descriptor slots currently allocated
Groups supplementary group list
NStgid descendant namespace thread group ID hierarchy
diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt
index fb0e1f2a19cc..7c871d6beb63 100644
--- a/Documentation/vm/transhuge.txt
+++ b/Documentation/vm/transhuge.txt
@@ -340,7 +340,7 @@ unaffected. libhugetlbfs will also work fine as usual.
== Graceful fallback ==
-Code walking pagetables but unware about huge pmds can simply call
+Code walking pagetables but unaware about huge pmds can simply call
split_huge_pmd(vma, pmd, addr) where the pmd is the one returned by
pmd_offset. It's trivial to make the code transparent hugepage aware
by just grepping for "pmd_offset" and adding split_huge_pmd where
@@ -414,7 +414,7 @@ tracking. The alternative is alter ->_mapcount in all subpages on each
map/unmap of the whole compound page.
We set PG_double_map when a PMD of the page got split for the first time,
-but still have PMD mapping. The addtional references go away with last
+but still have PMD mapping. The additional references go away with last
compound_mapcount.
split_huge_page internally has to distribute the refcounts in the head
@@ -432,10 +432,10 @@ page->_mapcount.
We safe against physical memory scanners too: the only legitimate way
scanner can get reference to a page is get_page_unless_zero().
-All tail pages has zero ->_refcount until atomic_add(). It prevent scanner
-from geting reference to tail page up to the point. After the atomic_add()
-we don't care about ->_refcount value. We already known how many references
-with should uncharge from head page.
+All tail pages have zero ->_refcount until atomic_add(). This prevents the
+scanner from getting a reference to the tail page up to that point. After the
+atomic_add() we don't care about the ->_refcount value. We already known how
+many references should be uncharged from the head page.
For head page get_page_unless_zero() will succeed and we don't mind. It's
clear where reference should go after split: it will stay on head page.
diff --git a/Documentation/vm/z3fold.txt b/Documentation/vm/z3fold.txt
new file mode 100644
index 000000000000..38e4dac810b6
--- /dev/null
+++ b/Documentation/vm/z3fold.txt
@@ -0,0 +1,26 @@
+z3fold
+------
+
+z3fold is a special purpose allocator for storing compressed pages.
+It is designed to store up to three compressed pages per physical page.
+It is a zbud derivative which allows for higher compression
+ratio keeping the simplicity and determinism of its predecessor.
+
+The main differences between z3fold and zbud are:
+* unlike zbud, z3fold allows for up to PAGE_SIZE allocations
+* z3fold can hold up to 3 compressed pages in its page
+* z3fold doesn't export any API itself and is thus intended to be used
+ via the zpool API.
+
+To keep the determinism and simplicity, z3fold, just like zbud, always
+stores an integral number of compressed pages per page, but it can store
+up to 3 pages unlike zbud which can store at most 2. Therefore the
+compression ratio goes to around 2.7x while zbud's one is around 1.7x.
+
+Unlike zbud (but like zsmalloc for that matter) z3fold_alloc() does not
+return a dereferenceable pointer. Instead, it returns an unsigned long
+handle which encodes actual location of the allocated object.
+
+Keeping effective compression ratio close to zsmalloc's, z3fold doesn't
+depend on MMU enabled and provides more predictable reclaim behavior
+which makes it a better fit for small and response-critical systems.